1. Field of the Invention
This invention relates to apparatus for driveshaft housings for boat engines or propulsion units generally and, in particular, for driveshaft housings connecting boat engines such as outboard, inboard-outboard and the like to the propeller. The apparatus is designed to protect humans, manatees, sea grass and the like in the water from the propeller, fins, and other parts of the housing, while also protecting the propeller, the fins and the like, and improving the efficiency of operation. This apparatus may be permanently or removably secured to such propulsion units.
This invention is an improvement upon the apparatus disclosed in applicant's U.S. Pat. No. 5,344,346, issued Sep. 6, 1994, and the disclosure, background and discussion of the prior art therein is incorporated herein by reference thereto.
2. Description of the Prior Art
The prior art has many examples of devices for protecting the propeller and submerged boat propulsion parts. However, these devices do not protect creatures in the water very well. Further, the prior art devices reduce the efficiency of the propulsion units by adding undesirable drag loads. Some of the prior art attachments are removable, which could reduce the drag load after reaching open water, but are really removable only when the boat is essentially in a dock or dry dock situation. Those that could be removed when the boat is under way or in open waters may lose attaching parts and/or are not as stable as desired to reduce vibration problems.
U.S. Pat. Nos. 1,009,635; U.S. Pat. No. 1,869,977; Re. 18,602; U.S. Pat. No. 2,054,374; U.S. Pat. No. 2,140,099; U.S. Pat. No. 2,355,842; U.S. Pat. No. 2,963,000; U.S. Pat. No. 2,985,133; U.S. Pat. No. 3,965,845 and U.S. Pat. No. 4,096,819 are examples of propeller guards that are essentially permanently attached in that they cannot be readily removed when the boat is under way or in open water. Removability is very desirable, because such guards are added drag loads.
Further, none of the devices protect creatures in the water very well. That is, fins or tines are spaced so far apart that arms, hands, fingers, fins, etc. can go between them and be damaged by the propeller. In some, the circle scribed by the propeller radius extends outside of the protection zone of the guard. In others, a keel-like support portion can do substantial impact damage to a swimming creature. Moreover, in some designs, the skeg or gear housing or other parts are forward of the protective zone and can do substantial impact damage. Finally, there are many sharp edges that are harmful, whether designed for cutting weeds or just sharp by the nature of their design.
U.S. Pat. No. 2,470,874 discloses a propeller guard that can be pivoted up out of the water. However, the fork arms provide no protection for swimmers and, in fact, are hazardous themselves because the fork arms have knife-like forward edges.
U.S. Pat. No. 2,972,977 discloses a propeller guard which affords more protection than some of the devices because an object engaging shoe is held behind and below the propeller by a pair of spaced, vertical support arms that are pivotally mounted on the transom. A push block carried about half-way down on the support arms pushes against the forward part of upper housing 16 to pivot the propeller and housing out of the water when the shoe strikes an object under the water.
However, the solid shoe adds a very substantial drag load that reduces the efficiency of the propulsion unit. While the device might be removed if the boat were dead in the water, it is very difficult because, after removal of the mounting from the transom, the unit must be lowered much further into the water so that the push block can be passed below the skeg. If the motor is running and the propeller is turning, removal is very dangerous because either one of the support arms or the push block may strike and damage the propeller. Thus, the outboard motor attachment is essentially permanently mounted because the boat must be either in dry-dock, or docked with the engine not running, for safe removal.
The shoe might have been designed to assist the boat in planing, either at full speed or at lower speeds in regulated waters. However, not only is there no teaching or suggestion that such was intended, but the upper part 52 of the shoe 50 has a reduced width to space the support arms apart. In addition, upper part 52 is angled toward the rear, so that when the boat is under way water passing over part 52 actually pushes the part 52 downwardly to interfere with any planing effort.
U.S. Pat. No. 2,319,640 discloses a propeller guard which provides a better protection zone than most. However, the blade-like fingers can cut and injure creatures in the water. Further, while the inventor states that his device reduces turbulence, there is still a substantial amount of drag load and turbulence and therefore less efficiency at slower speeds. Therefore it would be very desirable to be able to remove the device under way and in open water at higher speeds.
However, the guard is attached under the water line to the cavitation plate by a wing nut to a plate bolt. The device is subject to nut loosening and loss of the device as a result of the vibration of the blade-like fingers. To detach the guard, one has to work under water with the possibility of loss of the wing nut and/or guard. Moreover, the nut/bolt combination may corrode, resisting or preventing removal without tools. Thus, this propeller guard is again essentially a permanently mounted device which hampers efficiency at all speeds.
U.S. Pat. No. 4,565,533 discloses a propeller guard which does not provide adequate protection for swimmers, manatees, etc. because the rearwardly extending ribs are much too far apart. However, it does disclose a quick-release system to enable removal under way or in open water to improve propulsion efficiency at higher speeds when swimmers, manatees are not in, or not supposed to be in, the water. While a safety loop 46 on the main body is provided for attachment to a safety line to prevent loss by dropping the guard, the other essential part 44 of the attaching system does not have any means for preventing loss of the part. This is a major flaw since the boat may have to return through swimmer and manatee waters without protection for them.
This device has a further problem in that the ribs are going to vibrate, affecting the stability of the device and increasing turbulence. While a sleeve 38 is provided to receive the skeg, there is a substantial length of the main rib 25 between the skeg and a quick-release that isn't anchored in any way.
The structure of U.S. Pat. No. 4,565,533 includes a vertical main rib with a plurality of widely spaced side ribs extending laterally outwardly from the main rib and then substantially horizontally backwards to form an open cage around the propeller. The vertical and horizontal ribs cannot materially assist in urging a boat's stern upwardly to a more efficient operating position. Moreover, there is no suggestion or teaching in this patent regarding lifting a boat's stern. The three lower ribs 30, 30 and 32 are formed from resilient steel to provide shock absorbing functions. Thus, neither the function of protection of swimmers, etc. or the structure of applicant's invention is shown or taught.
U.S. Pat. No. 4,680,017 discloses a propeller guard that isn't satisfactory because of the large drag load, the damage that the sharp edges of ribs 58 can do to swimming creatures, and the inability to easily remove or reinstall the guard in open water or while under way--with the added possibility that the guard may be dropped in the water and lost. However, the device does show a frame member 52 which is channel shaped to extend around leading edge 18 of lower housing 16. This provides structural support for the ribs 58 and protects leading edge 18 and skeg 22 from damage. On the other hand, because water is flowing directly past frame 58 between ribs 58, there is no deflection of a swimmer or a manatee by a diverted water flow, and impact against the frame 58/edge 18 is direct and damaging.
U.S. Pat. No. 5,207,605 was cited during the prosecution of applicant's above-referenced U.S. Pat. No. 5,344,346 as teaching a tapered plate member. Kroeber was distinguished from that invention by noting that there was no disclosure in Kroeber of a plate member depending downwardly and rearwardly from a position forward of a gearshaft housing to divert swimmers, etc. around and under a housing and propeller.
The function of a propeller is to produce thrust along the axis of the propeller shaft to drive the boat or ship, by giving momentum to the water it displaces in an astern direction. In pushing the water backwards, a reaction force is developed to push the craft forward. It is therefore desirable to maintain the axis of the propeller substantially parallel to the horizontal axis of the craft when the hull is in its most efficient operating position in the water. Most craft that will be using this invention will have planing type hulls, as opposed to displacement hulls. The planing type hull operates most efficiently when the stern of the boat is raised by the speed of the boat in open waters.
As noted above, the prior art devices of this general type add drag load when used. Further, most of them cause substantial turbulence which further reduces the efficiency of the propeller. None of them react with the water passage to lift the stern of the boat to a more efficient operating position.
Applicant's previous invention in the above-referenced U.S. Pat. No. 5,344,346 solved the problems of protecting swimmers, sea grass, manatees, and other objects in the water by providing apparatus which was readily removed and reattached. Since it probably would be primarily used in speed restricted waters, and then removed in open water, it has worked very well.
However, in many coastal waters, there can be a series of alternately occurring open waters and speed restricted waters. Thus, to get a better efficiency in open waters many boaters may remove and reattach applicant's previous apparatus a number of times. It became apparent that an improved apparatus which provided improved efficiency in open water without removal would be very useful.
Accordingly, it is an object of this invention to provide apparatus which protects swimmers, sea grass, manatees and other objects in the water, while improving efficiency of propeller and boat hull operation.
It is another object of this invention to provide the improved apparatus just discussed while still providing protection for the propulsion units themselves.
It is a further object of this invention to provide such improved apparatus which is designed to improve the efficiency of the propulsion unit by admitting more water directly to the propeller area, while still providing lift to the stern of a boat to reduce the effect of any drag load.
A still further object of this invention is to provide such improved apparatus which may be removably or permanently secured to a propulsion unit.
Another object of this invention is to provide such improved apparatus which may be left in place at all times without appreciably affecting the performance of a boat.